Low-end cable set-top boxes (such as the Motorola DCT 2000 or Scientific Atlanta Explorer 2000) often display splices between two video clips poorly. Visual artifacts such as MPEG macroblocking, stuttering, and green flashes on the screen are common. The visual quality of splices on these low-end set-top boxes is generally poor because:
After the splice point, the presentation time of the first decoded frame (in the second video clip) does not match the expected frame presentation time, which is derived from the time base of the first video clip. This can cause the frame to be delivered to the analog video display circuitry part way through a frame refresh, producing analog video artifacts (such as the aforementioned green flash).
The MPEG decoder ignores both the transport layer discontinuity indicators and the Broken Link flag in the Group of Pictures header which immediately follows the splice, and decodes the first two B-frames in the second video clip. Decoding the B-frames at this point uses an incorrect reference frame (from the first video clip), resulting in digital video artifacts (such as the aforementioned macroblocking).